This invention relates to a method of regulating mucus secretions and fluid transport in the gastrointestinal system of a patient by administering purinergic receptor agonists such as certain uridine, adenine, or cytidine 5xe2x80x2-di- and triphosphates, dinucleoside polyphosphates and their analogs thereof.
There are many situations where it is therapeutically desirable to increase the amount of mucin secretion, bicarbonate secretions, and/or degree of hydration in gastrointestinal systems. The gastrointestinal system operates principally to extract energy and metabolic building blocks from the nutrient materials presented to it. The digestive tract includes the buccal cavity (primary salivary glands), esophagus, stomach, small intestine, large intestine, rectum, and ancillary organs (pancreas, liver and gall bladder). When the mucosal barrier is impaired in the digestive tract, it results in diseases such as dry mouth, gastro-esophageal reflux disease, peptic ulcer, inflammatory bowel disease, etc. Abnormal fluid and electrolytic transport in the lower gastrointestinal tract results in disorders such as constipation and diarrhea.
Mucus is a viscous material that coats many epithelial surfaces and is secreted into fluids such as saliva. It is composed chiefly of mucins and inorganic salts suspended in water. Mucus adheres to many epithelial surfaces, where it serves as a diffusion barrier against contact with noxious substances (e.g. gastric acid, digestive enzymes and bacteria) and as a lubricant to minimize shear stresses. Such mucous coatings are particularly prominent on the epithelia of the gastrointestinal, respiratory and genital tracts. Mucous is also an abundant and important component of saliva, giving it virtually unparalleled lubricating properties. Mucus-secreting cells such as goblet cells are abundant in the epithelium of the gastrointestinal tracts. Numerous submucosal mucous glands are scattered along the esophagus and especially accumulated below the upper and above the lower esophageal sphincters. Many of the acinar epithelial cells in salivary glands secrete mucus. The major structural molecules of the mucus layer are mucins, which are a family of large, heavily glycosylated proteins. The dense xe2x80x9csugar coatingxe2x80x9d of mucins gives them considerable water-holding capacity and makes them resistant to proteolysis, which may be important in maintaining mucosal barriers.
Bicarbonate secretion plays an important role in the maintenance of mucosal health in the gastrointestinal tract. The production of bicarbonate and mucus by the esophagus in response to local acidification provides an inherent mechanism for resisting acid-induced damage. The secretion of salivary protective factors, including bicarbonate, as well as bicarbonate secreted from esophageal submucosal glands, are important in preventing esophageal mucosal injury associated with gastrointestinal reflux disease. Mucosal bicarbonate also provides an important mechanism for protection against acid damage in the proximal duodenum, in which adherent mucus provides a stable protective layer supporting surface neutralization of acid by mucosal bicarbonate. [Nucleotides stimulate bicarbonate secretion in guinea pig pancreatic duct (Ishiguro el al 1999, J. Physiol. 519 Pt 2:551-558) and CFTR knockout mouse gall bladder epithelium (Clarke et al. 2000, Am. J Physiol. Gastrointest. Liver Physiol. 279:G132-138)].
Proper regulation of fluid and electrolytic absorption and secretion at appropriate regions along the gastrointestinal system is required for normal digestive function. Impairment of fluid transport leads to a variety of disorders, including constipation and diarrhea. Constipation is associated with a delay in the transit of fecal matter through the large intestine. The increased resident time of feces in the large intestine leads to increased fluid absorption by the colonic epithelium, and results in dehydration of feces and the subsequent production of dry, hard feces in the descending colon. Conversely, diarrhea results from rapid movement of fecal matter through the large intestine, resulting from either increased fluid secretion in the small intestine or by reduced fluid absorption in the colon.
Xerostomia, commonly known as dry mouth, results from the underproduction of saliva. Dry mouth is caused by radiation treatment or diseases that damage salivary glands and decrease salivary flow. Gastroesophageal reflux disease is the condition where the degree of exposure of esophageal mucosa to gastric contents is greater than normal. The most common manifestation is heartburn. Pharmacological treatment involves the use of H2 antagonists (e.g., Tagamet(copyright), Zantac(copyright), Pepcid(copyright), Axid(copyright)) and proton pump inhibitors such as Prilosec(copyright) or Prevacid(copyright), for treatment of acute disease. Peptic ulcer diseases include gastric ulcer, pyloric channel ulcer and duodenal ulcer. Ulceration results from a complex interplay of acid and chronic inflammation induced by Helicobacter pylori infection. Patients with duodenal ulcers have high acid secretion. Increased acid secretion causes changes in the wall of the duodenum, setting the stage for invasion by H. pylori. Drugs for treating peptic ulcer diseases include Histamine-2 (H2) blockers (Tagamet(copyright), Zantac(copyright), Axid(copyright), Pepcid(copyright), etc.), sucralfate, proton pump inhibitors, and antacids. Inflammatory bowel disease is classified into two types: ulcerative colitis and Crohn""s disease. Ulcerative colitis affects the colon/rectum and involves the mucosa or the innermost lining of the colon wall. Crohn""s disease is a transmural disease involving all layers of the bowel and may involve any part of the gut, from mouth to anus. Medical treatment of inflammatory bowel disease includes aminosalicylates and corticosteroids. Corticosteroids have substantial long-term toxicity. As an alternative to conventional therapies, medical researchers have sought to develop new treatments for gastrointestinal diseases.
The following references disclose the role of mucus integrity and mucin secretion in some diseases of the gastrointestinal tract. Rhodes et al. (Gut, 26:1312-1318 (1985)) suggested that colonic mucus undergoes continual desulphation and desialation in vivo as a result of faecal enzyme activity; altered susceptibility of colonic mucus may be important in the pathogenesis of colonic disease. Somasundaram et al. (Clin. Exp. Pharmacol. Physiol., 14:309-318 (1987)) report that the integrity of the gastric mucosa and its ability to secrete mucus are essential for protection of gastric mucosa against ulceration induced by aggressive factors active in any stress situation. Desai et al. (J. Pharm. Pharmacol. 47:734-738 (1995)) showed that SKF 38393, a specific dopamine D1-receptor agonist, was effective in preventing gastric and duodenal ulceration in rats. Sarosiek et al. (Digestion, 56 Suppl. 1 :15-23 (1995)) reported that the rate of secretion of esophageal mucin, EGF and PGE2, under the impact of HC1/pepsin in patients with reflux esophagitis, was significantly impaired. Saitoh et al. (Dig. Dis. Sci. 41:1768-1774 (1996)) showed that compared with healthy subjects, the total yields of mucin from ulcerative colitis patients were low due to a deficiency of neutral mucin, whereas those from Crohn""s disease patients were high due to high-molecular weight mucin. Sarosiek et al. (Gastroenterology, 10:675-681 (1996)) suggest that an increase in the secretion rate of inorganic and organic protective components in saliva may be useful to the treatment of gastroesophageal reflux disease. Zeeh (Gastroenterology, 110:1 077-1083 (1996)) reported that administration of keratinocyte growth factor ameliorates mucosal injury in an experimental model of colitis in rats. Abbas et al. (Indian J Exp. Biol. 36:182-186 (1998)) report that the antiulcerogenic effect of GABA and baclofen may be due to their predominant effects on mucosal defensive factors like enhanced mucin secretion and decreased cell shedding or mucosal damage. Nath et al. (Clin. Exp. Pharmacol. Physiol. 25:564-567 (1998)) report that polyriboinosinic-polyribocytidylic acid had a potent anti-gastric ulcer effect on rats; polyriboinosinic-polyribocytidylic acid was shown to cause a decrease in free and total acid and pepsin and an increase in mucin content in Shay rat. Newton et al. (Gut, 43:470-475 (1998)) report that H. pylori in vivo causes structural changes in the adherent gastric mucus layer but the mucus barrier thickness is not compromised.
The following references disclose the compositions of purinergic receptor agonists and/or treatment of diseases. Uridine 5xe2x80x2-triphosphate has been shown to increase both the rate and total amount of mucin secretion by Goblet cells in vitro (Lethem et al., Am. J. Respir. Cell Mol. Biol., 9:315-322 (1993)). U.S. Pat. No. 5,900,407 (Yerxa et al.) discloses a method for the stimulation of tear secretion in a subject in need of treatment. The method comprises administering to the ocular surfaces of the subject a purinergic receptor agonist such as uridine 5xe2x80x2-triphosphate, cytidine 5xe2x80x2-triphosphate, adenosine 5xe2x80x2-triphosphate, or their analogs and derivatives, in an amount effective to stimulate tear fluid secretion. U.S. Pat. No. 5,837,861 (Pendergast et al.) discloses P2Y2 purinergic receptors of dinucleoside polyphosphates having structure of Formula I, wherein X is oxygen, methylene, or difluoromethylene; n=0 or 1; m=0 or 1; n+m=0, 1 or 2; and B and Bxe2x80x2 are each independently a purine residue or a pyrimidine residue linked through the 9- or 1-position. The compounds are useful in the treatment of chronic obstructive pulmonary diseases, bronchitis, certain pneumonias, cystic fibrosis, sinusitis, and otitis media. U.S. Pat. No. 5,763,447 (Jacobus et al.) discloses a method of promoting drainage of mucous secretions in the congested airway of an immobilized patient. The method comprises administering to the airway of the patient a uridine phosphate such as uridine 5xe2x80x2-triphosphate (UTP), or P,1P4 -di(uridine-5xe2x80x2)tetraphosphate, in an amount effective to promote drainage of fluid in the congested airway, including sinuses, by hydrating mucous secretions or by stimulating ciliary beat frequency in the airway. U.S. Pat. Nos. 5,789,391, 5,981,506, 5,972,904 and 5,958,897 are directed to a method of promoting drainage of congested mucous secretions in the sinuses of a subject in need. The method comprises administering to the sinuses of the subject a uridine phosphate such as uridine 5xe2x80x2-triphosphate (UTP) or P1, P4-di(uridine-5xe2x80x2) tetraphosphate, an analog of UTP, or any other analog, in an amount effective to promote drainage of congested fluid in the sinuses by hydrating mucous secretions or by stimulating ciliary beat frequency in the sinuses. U.S. Pat. No. 5,968,913 is directed to a pharmaceutical compositions of UTP for use in promoting increased mucociliary clearance of retained mucous secretions of the human airways, middle/inner ears or sinuses. U.S. Pat. No. 5,763,447 is directed to a method of preventing or treating pneumonia, including ventilator-associated pneumonia, in a bedridden or immobilized subject in need of such treatment. The method comprises administering to the airways of the patient a uridine phosphate such as uridine 5xe2x80x2-triphosphate (UTP), P1, P4 -di(uridine-5xe2x80x2)tetraphosphate, or their analogs, in an amount effective to promote drainage of fluid in the congested airways. WO 99/09998 discloses a method of using uridine 5xe2x80x2-diphosphate and analogs thereof to treat lung disease. The compounds described in the above references (""391, ""506, ""904, ""897, ""913 and ""447 Patent and WO 99/09998), which have purinergic receptor activity, are incorporated herein by reference. U.S. Pat. No. 5,733,916 (Neely) discloses a method of preventing or treating ischemia-reperfusion injury or endotoxin-related lung injury by administration of a composition containing a selective Al adenosine receptor antagonist and/or a P2X purinoceptor antagonist. Somers et al. (Laboratory Investigation, 78:1375-1383 (1998)) report that P2Y6 receptor was highly expressed in the T cells infiltrating active inflammatory bowel disease, whereas P2Y6 expression was absent from the T cells of unaffected bowel. Boyer et al., (Br. J. Pharmacol. 118:1959 (1996)) synthesized and tested a series of chain-extended 2-thioether derivatives of adenosine monophosphate (AMP) as agonsists for activation of the phospholipase C-linked P2Y-purinoceptor of turkey erythrocyte membranes, the adenylyl cyclase-linked P2Y-purinoceptor of C6 rat glioma cells, and the cloned human P2U-receptor stably expressed in 1321N1 human astrocytoma cells.
Specific dinucleoside phosphate compounds known in other prior art are listed in Table I, along with their corresponding references. These compounds have not been used in the prior art to increase the mucus secretion or to correct for fluid and electrolytic imbalance in the gastrointestinal tract, and Applicants intend to include them in this invention.
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P2Y purinergic receptors are purine and pyrimidine nucleotide receptors that couple to G proteins; they are 308 to 377 amino acid proteins with molecular weights of 41 to 53 kDa after glycosylation. P2Y receptors such as P2Y1, P2Y2 and P2Y6 receptors are present in the gastrointestinal tract (Ralevic et al., Pharm. Rev. 50:415-492 (1998)). Because of the demonstrated ability of purinergic receptor agonists to stimulate mucus/mucin secretion in and around the eye (U.S. Pat. No. 5,900,407), and in lung and sinuses (U.S. Pat. No. 5,837,861), Applicants were motivated to investigate whether P2Y purinergic receptor ligands could affect mucus and/or mucin secretion, and to correct abnormal fluid transport in the gastrointestinal tract, and thus be effective in treating diseases and disorders of the upper and lower gastrointestinal tract.
Applicants have discovered that all P2Y receptors, including P2Y4 and P2Y11 are present in gastrointestinal tissues. Applicants also discover that mucus and mucin secretion, bicarbonate secretion and fluid transport in these tissues can be regulated via P2Y purinergic receptor-mediated mechanisms. P2Y purinergic receptor ligands, administered orally or systemically, provide a novel method of treating gastrointestinal disorders.
The invention provides a method of regulating mucus/mucin secretions, and fluid transport in the gastrointestinal tract. The invention provides a method for treating gastrointestinal disease in which the mucosal barrier of the gastrointestinal system is impaired. The invention additionally provides a method for correcting disorders of fluid secretion or absorption in the gastrointestinal tract resulting in either diarrhea or constipation. The method comprises administering to a patient a pharmaceutical composition comprising a purinergic P2Y receptor ligand, in an amount effective to regulate mucus/mucin and bicarbonate secretions and fluid transport in the gastrointestinal tract. Methods of administering include oral and systemic administration. The diseases treated include diseases and disorders of the buccal cavity, esophagus, stomach, small intestine, large intestine, rectum, and ancillary organs such as pancreas, liver and gall bladder.
The pharmaceutical composition used in this invention comprises a P2Y purinergic receptor agonist. P2Y agonists increase secretion of water, bicarbonate and mucin in the mucosal epithelia of the gastrointestinal tract. P2Y agonists include uridine 5xe2x80x2- di-and triphosphate (UDP, UTP) and their analogs (Formulae Ia and Ib), adenosine 5xe2x80x2-monophosphate (AMP) and its analogs, adenosine 5xe2x80x2- di-and triphosphate (ADP, ATP) and their analogs (Formulae IIa and IIb), cytidine 5xe2x80x2- di-and triphosphate (CDP, CTP) and their analogs. (Formulae IIIa and IIIb), and dinucleoside polyphosphate compounds (general Formula IV).